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Calculators

Syndet & shampoo bars

Surfactants are sold as solutions, not neat. Twenty grams of a 30 % betaine is six grams of surfactant and fourteen of water, and every shampoo-bar recipe online is written in raw-material weights that leave that conversion to you. This does it, both ways round.

Surfactants

The active percentage is on your supplier’s data sheet for the exact grade you bought. SCI alone is sold at 65, 78 and 85 %, so there is no default.

Everything else

Butters, fatty alcohols, starch, conditioner, fragrance. Give the water content of anything liquid.

add a surfactant with its active percentage

Calculated at soapformulator.com, every value sourced. Check the figures against your own scale.

The formula, and where it comes from 
activeᵢ      = massᵢ × active %ᵢ ÷ 100
actives %    = Σ activeᵢ ÷ total × 100
ratio        = Σ anionic actives ÷ Σ amphoteric actives   # by active, not by weight
water        = Σ(massᵢ × water %ᵢ ÷ 100)
  • Active matter is the mass fraction of a raw material that is surfactant, as stated on the supplier’s technical data sheet. Active mass = raw-material mass × active % ÷ 100; the blend’s active matter is the sum of those over the total mass. — The active percentage belongs to a specific grade from a specific supplier. The same chemical is sold at several strengths, so the figure must come from the data sheet for the material actually used.
  • Anionic and cationic surfactants carry opposite charges and associate into a neutral complex of low water solubility. Depending on the ratio this precipitates, thickens, or is used deliberately as the coacervate that deposits conditioning polymer on hair. — Whether the interaction is a fault or the point depends on the materials and the ratio. A cationic conditioning surfactant in an anionic shampoo bar reduces foam and can leave the bar grainy; a cationic polymer at low level is how conditioning shampoos work.
  • Water carried into the batch by liquid surfactants and other ingredients, from each raw material’s stated water content: water = Σ(massᵢ × waterᵢ % ÷ 100). — A liquid surfactant’s non-active fraction is mostly but not entirely water; salt and preservative make up the rest. Use the data sheet’s water figure where it gives one.

Why there is no mildness score

The measurements of mildness that exist — the zein test, the collagen swelling test, patch testing — are laboratory tests on a finished product. Nobody has published a model that turns a blend’s composition into one, so any score here would be invented. The charge split is real, and it is what those tests mostly track: amphoterics and non-ionics soften an anionic blend.

Water in a bar that has to set

Liquid surfactants carry most of their weight as water. A shampoo bar with a generous pour of betaine can end up with more water in it than the maker ever added on purpose, and it stays soft or sweats. The water figure here counts every raw material whose water content you give, and says when it is a floor because you left one out.

Common questions

Where do I find the active percentage?
On the supplier’s technical data sheet, usually as "active matter", "active content" or "solids". Sometimes the grade name carries it — an SCI sold as "85" is 85 % active. If a shop does not publish it, ask; a surfactant sold without one is a surfactant you cannot formulate with.
What anionic to amphoteric ratio should I aim for?
There is no published figure to aim at, and the ones that circulate are habits of the craft. What is real is the direction: more amphoteric softens the blend and thickens the lather, at the cost of some cleansing. The page gives the ratio by active matter, which is the only way the number means anything — by raw weight a 30 % betaine looks three times bigger than it is.
Can I put a conditioner in a shampoo bar?
Conditioning ingredients are mostly cationic, and cationics pair with anionics into a complex that dissolves poorly. At low levels that is how conditioning shampoos deposit on hair; at the levels a conditioner bar uses, it usually costs foam and can make the bar grainy. The page warns whenever the two charges meet so you can decide which it is.
What is the fragrance limit for a shampoo bar?
Shampoo is IFRA category 9, rinse-off, the same as bar soap. The figure is on your supplier’s certificate of conformity for each fragrance; the fragrance and allergens page works it out against the finished weight.

Goes well with

All tools
Lotions & creams Phases, q.s. to 100 %, usage rates, and the HLB your oils actually need
Fragrance & allergen check IFRA load by product type and EU/Canada allergen declarations from supplier sheets

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